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Managing diffuse pollution from farmyards with wetlands: implications for water quality and ecology

This study examines the use of wetlands as a low-cost and sustainable solution for managing diffuse pollution from farmyards. Findings suggest that wetlands can effectively reduce contaminants and improve water quality, while also enhancing biodiversity. The research highlights the importance of pre-treatment, natural colonization of vegetation, and varied water depths in maximizing treatment efficiency. These findings have significant implications for addressing diffuse pollution and promoting sustainable agricultural practices.

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Managing diffuse pollution from farmyards with wetlands: implications for water quality and ecology

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  1. Managing diffuse pollution from farmyards with wetlands: implications for water quality and ecology Caroline Coletto (now Enviros Consulting Ltd.) Kevin Stewart Kate Heal School of GeoSciences The University of Edinburgh, Scotland

  2. Many drivers for addressing diffuse pollution: water quality and ecosystem degradation, health concerns, economic costs 65% of Scottish rivers at risk of failing WFD due to diffuse pollution from agriculture and forestry activities Farmyard runoff is a potential source of contaminants Diffuse pollution expected to become worse as result of climate change Wetlands = low-cost sustainable solution Why are farm wetlands required?

  3. Wetlands on 7 farms in River Tweed catchment, Scottish Borders CW2 CW1 Surface areas = 400-1550 m2 Water volumes = 130-1400 m3 CW7 CW3 CW4 CW6 CW5

  4. Methods • Water sampling at inlet and outlet • pH, conductivity, TSS, BOD, reactive P, NO3/NO2, NH4-N • National Pond Survey methodology • Macrophyte walk-over survey -> dominant species • Macroinvertebrate survey: 3-minute kick-sampling divided between 6 meso-habitats in each wetland • Biodiversity indicators • Species richness, species rarity index (SRI), conservation value (CV) • Average score per taxon (ASPT) for macroinvertebrate data • Simpson and Shannon indices of diversity and evenness

  5. Water chemistry results (1) Reduction in over-deep pond

  6. Water chemistry results (2) Reduction of NO3 to NH4-N in over-deep pond

  7. % reduction by concentration from inlet to outlet Over-deep pond Relatively clean inflow water

  8. Outlet concentrations compared with threshold values

  9. Ponds with series of basins retain SS CW2 CW7

  10. Poor water treatment in ponds poorly implemented/high inflow concentrations CW4: Field drain 15 m from inlet => short-circuiting CW6: Design misinterpreted => water depth 3 m instead of 1.5 m

  11. Iris pseudacorushttp://www.botanik.uni-karlsruhe.de/garten/fotos-knoch/Iris%20pseudacorus%20Sumpf-Schwertlilie%201.jpg Macrophytes Celery-leaved buttercup http://farm4.static.flickr.com/3467/3285752114_94d8aefb08.jpg?v=0 Common reed http://siera104.com/images/bio/ecology/Phragmites%20australis16-05-04.jpg Macroinvertebrates Freshwater snail http://www.weichtiere.at/images/weichtiere/schnecken/succinea/hydrobiidae_1_300.jpg Water boatman http://www.cals.ncsu.edu/course/ent425/spotID/Heteroptera/notonect01.jpg Stonefly nymph http://academics.smcvt.edu/Vermont_rivers/River%20sites/Images%20for%20Site/Alloperla_concolor,I_DSC56.jpg Water beetle http://www.toyen.uio.no/fagene/zoologi/insekter/ekle_kryp/images/insekter/dytiscidae.jpg

  12. Wetland vegetation Aquatic macroinvertebrates

  13. Main findings and recommendations • Highest treatment efficiencies – CW1, 2 & 7 • Highest biodiversity values – CW 1, 4 & 7 • Common features of high-performing wetlands • ≥ 3 wetland cells within system • Pre-treatment, e.g. settlement zones • Natural colonisation or planting of vegetation • Varied water depths • Treatment efficiency expected to increase as wetlands mature

  14. Concluding remarks • Further research: • Link between water chemistry and ecology • Flood attenuation • Pollution swapping (increased CH4 and N2O emissions) depends on magnitude of N inputs • Wetlands could offset expected increase in diffuse pollution as result of climate change

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